A.Asynchronous Transfer Mode （ATM）
B.data-link switching （DLSw）
C.Route Processor Redundancy （RPR）
D.Frame Relay （FR） 
E.Metro Ethernet
F.Multiprotocol Label Switching （MPLS）

A.a class can be identified as a single application， multiple applications with similar service needs，or be based on the source or destination IP address
B.a drawback of the DiffServ field in the MAC header to mark frames into behavior aggregates （BAs）
C.DiffServ uses the DiffServ field in the MAC header to mark frames into behavior
D.the DiffServ field occupies the same eight bits of the MAC header that were previously used for the ToS field
E.the first six high-order bits of the DiffServ field are used to identify the Resource Reservation Protocol （RSVP） value
F.the primary goal of DiffServ is scalability